Periodontal diseases, ranging from gingivitis to more severe forms of periodontitis, are initiated by a bacterial infection followed by a host response that may lead to a highly degenerative oral disease including tooth loss and tissue damage (Page, R. C. (1998) Ann. Periodontol. 3, 108). The current treatments of periodontal diseases, which affect a large percentage of the population, involve primarily the use of compositions containing antimicrobial compounds or various non-steroidal antiinflammatory agents (NSAIDs).
Although bacteria appear to be essential for the causation of periodontitis, progression of periodontal disease is dependent on the host response to pathogens that colonize the tooth surface (Hart, T. C., et al. (1994) J. Periodontol. 65, 521). In turn, periodontal disease can be controlled chemotherapeutically by uncoupling host-mediated destruction rather than reducing the etiological load (Offenbacher, S. et al. (1993) J. Periodontol. 64, 432). Along these lines, a body of evidence has identified the inhibition of PGE2 formation and its presence at gingival sites as being relevant therapeutic interventions. For example, PGE2 generation from gingival homogenates is significantly inhibited by flurbiprofen (ElAttar, T. M. A., et al. (1984) J. Periodontol. 55, 536), and COX-derived eicosanoids in crevicular fluid (CF) are decreased in animals taking flurbiprofen (Smith, M. A., et al. (1993) Infection and Immunity 61, 1453; Offenbacher, S., et al. (1989) J. Periodontal Res. 24, 63). Flurbiprofen also reduced CF-PGE2 levels, gingival inflammation, tooth attachment loss and bone loss, and in some cases resulted in bone gain (Pauletto, N. et al. (1997) J. Can. Dent. Assoc. 63, 824). In humans, flurbiprofen dramatically decreased the CF-PGE2 levels (Abramson, M. M. et al. (1992) J. Periodont. Res. 27, 539). These findings suggest that NSAIDs may exert their pharmacological action of inhibiting COX derived proinflammatory eicosanoids within the periodontium and suggest that novel anti-inflammatory agents might be useful in managing periodontal diseases.
Polymorphonuclear leukocytes (PMN, neutrophils) are the most abundant immune cells recruited to early inflammatory periodontal lesions and are the most numerous host cells within the periodontal tissues (Hart, T. C., et al. (1994) J. Periodontol. 65, 521). The presence of Gram-negative oral pathogens represents the primary etiologic factor, however, the progression of periodontal disease is dependent on the host response to pathogenic bacteria that colonize the tooth surface. Hence, recruitment of PMN followed by aberrant release of inflammatory mediators not only contributes to the onset of periodontal disease and is associated with rapid and widespread tissue destruction (Daniel, M. A., et al. (1996) J. Periodontol. 67, 1070), but can also be further amplified by the release of an array of inflammatory mediators by neutrophils within the periodontium.
It is well known that PMN participate in host defense against bacterial infections and are also involved in noxious inflammatory reactions (Weiss, S. J., et al. (1981) J. Clin. Invest. 68, 714; Babior, B. M. (1984) Blood 64, 959). Recruitment of neutrophils to the periodontium contributes to the progression of periodontal disease and to the destruction of periodontal tissues (Page, R. C. (1998) Ann. Periodontol. 3, 108; Daniel, M. A., et al. (1996) J. Periodontol. 67, 1070).
Several inflammatory mediators such as cytokines, chemokines and metalloproteases are associated with periodontal disease (Romanelli, R., et al. (1999) Infect. Inmun. 67, 2319; Gainet, J., et al. (1998) Lab. Invest. 78, 755; Assuma, R., et al. (1998) J. Immunol. 160, 403). Other prominent mediators are the arachidonic acid derived products, including leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) (Offenbacher, S. et al (1986) J. Periodontal Res. 21, 101). Indeed, many of the pathophysiological events that occur in periodontal diseases can be explained to a large extent by the activities of lipid mediators (Solomon, L. M., et al. (1968) J. Invest. Dermatol. 51, 280; Raisz, L. G., et al. (1974) Prostaglandins 8, 377; Klein, D. C., et al. (1970) Endocrinology 86, 1436; Crunkhorn, P., et al. (1969) Br. J. Pharmacol. 36, 216; Collier, J. G., et al. (1972) Br. J. Pharmacol. 44, 374). For example, LTB4, a well appreciated and potent chemoattractant, also initiates the accumulation of leukocytes within inflamed sites, stimulates the release of granule-associated enzymes (Borgeat, P., et al. (1990) Clin. Biochem. 23, 459) and was recently found to stimulate bone resorption (Traianedes, K., et al. (1998) Endocrinology 139, 3178).
Along these lines, PGE2 is a very potent stimulator of bone loss, which is held to be a hallmark of periodontal disease (Zubery, Y., et al. (1998) Infect. Immun. 66, 4158). PGE2 is also well appreciated for its ability to directly mediate vasodilation, increase vascular permeability, enhance pain perception by bradykinin and histamine, alter connective tissue metabolism, and enhance osteoclastic bone resorption (Tsai, C.-C. et al. (1998) J. Dentistry 26, 97). The levels of PGE2 are significantly elevated in the crevicular fluid (CF) of patients with periodontal infections, especially localized juvenile periodontitis, when compared to healthy sites. These levels correlate with disease severity and aggressiveness and constitute a reliable indicator of ongoing clinical periodontal tissue destruction (Offenbacher, S., et al. (1984) J. Periodontal Res. 19, 1). CF-PGE2 levels can also be used to predict future acute loss of periodontal attachment (Offenbacher, S., et al. (1986) J. Periodontal Res. 21, 101).
Pathophysiological responses that occur in periodontal diseases, including inflammatory cell recruitment, edema, pain, bone resorption and collagen destruction, can be mediated for the most part by effector molecules originating from the arachidonate cascade (Solomon, L. M. et al. (1968) J. Invest Dermatol. 51, 280; Raisz, L. G., et al. (1974) Prostaglandins 8, 377; Klein, D. C., et al. (1970) Endocrinology 86, 1436; Crunkhorn, P., et al. (1969) Br. J. Pharmacol. 36, 216; Collier, J. G., et al. (1972) Br. J. Pharmacol. 44, 374). In particular, considerable evidence has demonstrated the importance of PGE2 in the pathogenesis of periodontal diseases. In vitro, PGE2 increases osteoclast numbers and bone resorption (Lader, C. S., et al. (1998) Endocrinology 139, 3157), decreases proteoglycan synthesis and increases metalloprotease production by cultured chondrocytes (Debrumfernandes, A. J., et al. (1996) Br. J. Pharmacol. 188, 1597). Bone resorption in vivo caused by three periodontal pathogens is mediated in part by PGE2, causing tooth attachment loss and bone loss (Zubery, Y., et al. (1998) Infect. Immun. 66, 4158). Prior to these findings, PGE2 was proposed as a reliable molecular indicator of ongoing periodontal tissue destruction that might be used to predict future acute periodontal attachment loss (Offenbacher, S., et al. (1986) J. Periodontal Res. 21, 101).
Prostaglandin endoperoxide synthase (cyclooxygenase, COX) catalyzes two reactions by which arachidonic acid is converted to PGH2, the common precursor of all prostanoids including PGE2. To date, two COX isoforms are known (Smith, W. L., et al. (1996) J. Biol. Chem. 271, 33157). COX-1 appears to support the levels of prostanoid biosynthesis required for maintaining organ and tissue homeostasis (Smith, W. L., et al. (1996) J. Biol. Chem. 271, 33157; Vane, J. R., et al. (1996) Scand. J. Rheumatol. 102, 9), whereas COX-2 expression appears to be restricted in basal conditions within most tissues and is up-regulated during inflammation or stress in a wide range of tissues (O'Banion, M. K., et al. (1992) Proc. Natl. Acad. Sci. USA 89, 4888; Seibert, K., et al. (1994) Proc. Natl. Acad. Sci. USA 91, 12013; Needleman, P., et al. (1997) J. Rheumatol. 24, 6). The finding that homogenates of inflamed periodontal tissues display an increased PGE2 synthetic capacity when compared to homogenates from healthy tissues suggests an increased COX activity is associated with periodontal tissues (ElAttar, T. M. A. (1976) Prostaglandins 11, 331; Albers, H. K., et al. (1979) Dtsch. Zahnarztl. Z. 34, 440; ElAttar, T. M. A., et al. (1982) Prostaglandins Leukot. Med. 8, 447; ElAttar, T. M. A., et al. (1984) J. Periodontol. 55, 536). Moreover, given the clearly deleterious actions of PGE2 on the integrity of tissues of the periodontal pocket, both the potential involvement of the inducible COX isoform (COX-2) in periodontal disease and potential role of novel lipid mediators are of interest in the pathogenesis of periodontal disease.
Lipoxins (LX) and aspirin-triggered LX (ATL) are arachidonic acid-derived bioactive lipids that are formed by interactions between individual lipoxygenases (LO) and appear to play an important role in downregulating neutrophil responses in inflammation (Serhan, C. N. (1997) Prostaglandins 53, 107). In the nanomolar range, LXA4 and its 15R epimer (15-epi-LXA4) triggered by aspirin each inhibit fMLP- and LTB4-stimulated PMN adhesion and transmigration and hence represent potential counterregulatory signals operative in the resolution of inflammatory sites (Serhan, C. N. (1997) Prostaglandins 53, 107; Serhan, C. N., et al. (1996) FASEB J. 10, 1147; Takano, T., et al. (1997) J. Exp. Med. 185, 1693; Serhan, C. N. et al. (1995) Biochemistry 34, 14609). Like most autacoids and lipid mediators, LX are rapidly generated, act within a local microenvironment, and are rapidly enzymatically inactivated. The roles of LX and ATL roles in vivo, were studied by using metabolically stable LX and ATL analogs that were designed to resist rapid enzymatic inactivation and mimic the in vitro actions of naturally occurring LX and ATL (Serhan, C. N., et al. (1995) Biochemistry 34, 14609).
In addition to confirming the presence of LTB4 and PGE2, (Tsai, C.-C. et al. (1998) J. Dentistry 26, 97), it was shown for the first time that LXA4 is produced by activated neutrophils from LJP patients. It was also shown that LXA4 is present within the crevicular fluid from periodontitis patients with active disease. These results are the first demonstration that LJP peripheral blood neutrophils are in a primed state for LX generation. This in vivo “priming” for up-regulated lipoxin profiles was also observed with neutrophils isolated from asthmatic patients (Chavis, C., et al. (1996) J. Exp. Med. 183, 1633) and can be mimicked in vitro with cytokine-priming of neutrophils from healthy donors (Fiore, S., et al. (1990) J. Exp. Med. 172, 1451).
It was recently reported that LXA4 and ATL analogs reduce leukocyte trafficking stimulated by TNF-α while concomitantly re-orientating the cytokine-chemokine axis towards an anti-inflammatory profile (Hachicha, M., et al. (1999) J. Exp. Med. 189, 1923). LX-ATL can thus protect host tissues via multilevel regulation of proinflammatory signals.
Periodontal disease has implications beyond the deleterious effects on oral tissues and structural integrity. Thus, periodontitis represents a potential risk factor for increased morbidity or mortality for several systemic conditions including cardiovascular diseases, pregnancy complications, and diabetes (Page, R. C. (1998) Ann. Periodontol. 3, 108; Garcia, R. I., et al. (1998) Ann. Periodontol. 3, 339). Of great importance in this context, is the finding that the systemic presence of P. gingivalis up-regulates the expression of COX-2 (heart and lungs; FIG. 6) which is a marker of on-going inflammation (Herschman, H. R. (1998) Trends Cardiovasc. Med. 8, 145).
The recognition of the endogenous and multifaceted anti-inflammatory role of the lipoxins (Serhan, C. N. (1994) Biochim. Biophys. Acta, 1212, 1; Serhan, C. N. (1997) Prostaglandins 53, 107), combined with the findings that both lipoxin A4 and lipoxin B4 are rapidly deactivated by dehydrogenation (Serhan, C. N.; et al. (1993) Biochemistry, 32, 6313; Maddox, J. F. et al. (1998) FASEB J., 12, 487) or ω-oxidation (Sumimoto, H. et al. (1993) FEBS Lett., 315, 205; Mizukami, Y. et al. (1993) Biochim. Biophys. Acta, 1168, 87; Mizukami, Y. et al. (1994) Eur. J. Biochem, 224, 959), led to the design and synthesis of a number of LX analogs with increased biostability (Serhan, C. N. et al. (1994) Biochemistry, 34, 14609). Several LX analogs of this type were reported to have interesting biological properties and therapeutic potential (Serhan, C. N. et al. (1994) Biochemistry, 34, 14609; Takano, T. et al. (1998) J. Clin. Invest. 101, 819). The use of lipoxin analogs for the treatment and prevention of periodontal disease as well as related systemic diseases, however, has not been described previously.